ORA-12317: logon to database (link name string) denied

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ORA-12317: logon to database (link name string) denied
Cause: There are severalpossible causes for this error. First, you can get this error
if your username (and password, if you are using database instead of operating
system authentication) in the secondary database are not identical to your
username (and password) in the primary database. Second, you can get this error
if your username in the secondary database is invalid (has not been created).
Third, you can get this error if the username/password combination specified in
the connect string of the database link definition is invalid (either not createdor
has an invalid password).
Action: In the first case,ensure that the secondary database contains a username
(and password, if you are using database authentication) identical to the oneyou
are using in the primary database. In general, you should always use operating
system authentication in Trusted ORACLE (see the Trusted ORACLE RDBMS
Guide to Security Features for more information about the advantages of OS
authentication). In the second case, ensure that your username in the secondary
database has been created. In the third case, ensure that the usernamespecified in
the connect string has been created in the secondary database.